Still interested in purely-radiant cooling.

Hi:
Please don't get upset at me. I posted something similar recently but
it didn't describe it properly.
I thinking of a cooling mechanism for houses and building in which the
cooling -- in the direct sense -- involves only radiation and no
convection at all. Sorta like a radiant-stove-top in reverse.
Indirectly, however, some amount of convection and conduction will be
needed [liquid helium, cold metals]. The cooling panel is the ceiling
and cools objects below it.
My visualization is that the radiant cooling panel contain extremely
cold metallic coils [cooled by liquid helium to almost absolute zero],
this would probably be deepest part of the panel.
http://en.wikipedia.org/wiki/Liquid_helium
Here, another question arises. Which is better to use -- Helium-3 or
Helium-4? Which one would have a stronger cooling effect if both were
at the same temperature?
The radiant cooling panel is the ceiling. It has 3 layers.
Layer 1: a material that allows heat radiation to pass through but is
a very poor conductor of heat
Layer 2: the same material found on the very top of radiant stove
tops
Layer 3: this is the deepest part containing the cool metallic coils.
Inside these coils are where the liquid helium would be flowing
through]
Layers 2 & 3 don't have any air molecules around them. The cold metal
coils are in a vacuum so they are not exposed to any air that would
solidify/liquefy. This means the space between layer 1 & 2 is also a
vacuum free of air.
There is dehumidification which is separate from the cooling.
Dehumidification is done by air processing devices on walls -- left,
right, back, front. These walls give out and take in air. There is
both re-circulation and fresh air. For fresh air, all vapors molecules
are let into the room -- excluding H20, CO2, gases with odors, toxic
vapors [such as CO], dust, irritating vapors, smoke or allergens. For
re-circulation, air in the room is sucked, cleaned [i.e. H20, CO2,
toxic vapors [such as CO], dust, irritating vapors, smoke and
allergens are removed] and then blown back into the room. In either
case, the amount of air-molecules-per-second-per-square-meter that is
sucked out of the room is the same is the amount of air-molecules-per-
second-per-square-meter the is blown into the room -- and visa versa.
Hence, the subject in the room doesn't feel any sucking or blowing.
The result is that the room now contains only N2 and O2 -- if you
exclude the CO2 and H2O-vapor emitted from the living subject[s]. The
N2 and O2 are kept at no less than least 70 degress Fahrenheit -- via
convection heating if the ambient temperature is less than 70 F -- to
prevent them from liquefying or solidifying. I know it's ironic that
the air would have to be heated in order to assist in preventing the
radiant cooler from failing. Still interesting, though.
Yes, heat absorbed into the radiant cooling panels is carried off
using convection -- but this is not what the subject inside the room
feels. The direct cooling effect on anything/anyone inside the room is
radiant.
Can anyone suggest a better manner for direct radiant cooling? If so,
please explain
By direct radiant cooling, I mean that if you place your body at a
noticeable distance from from panel, you'll feel cold because the
extreme cold of the coil will draw IR radiation away from your body.
OTOH, if you touch the panel, you won't feel as cold because the 1st
layer of the panel is a very poor conductor of heat.
On the ceiling, layer 1 is the lower than layer 2. Layer 3 is the
highest.
Thanks a bunch,
Radium

Maybe if you told us what the intended application is.....
I can't even visualize any application where it would be cost effective to
use a system like that. Just the liquid helium would make it cost
prohibitive.

Why would frostbite occur? The lowest layer [the one a body part would
most likely contact] is an extremely poor conductor of heat, so it
wouldn't feel that cold. It's the radiant cooling, that would feel
cold.

Sounds like you are describing something that is in every kitchen: a
residential freezer. It too is very cold inside, but has "an extremely poor
conductor of heat" (an insulator) on the outside "where it is most likely to
come into contact" with any heat source.
How well does the outside wall of that freezer collect the heat radiated
from your body when you are a few feet or even a few inches away?
While I think that innovation starts with "outside the box" thinking, I
believe that it still must be based on the laws of THIS universe.
Bob

No. It works primarily via convection. Even the old 'cold
plate' fan-less ones ( as slow as they were to cool ).

Once the heat is radiated from your body, it is gone ( to you
). It's not going to turn around and come back if it fails to find a
place to go.
Also, ;picture standing in front of a campfire - your face can
get too hot, while your ass freezes.
A very small percentaqe of the heat you radiate goes in any
one particular direction, and the amount that falls on the 'receiving
/ absorbing surface' will thusly decrease as the square of the
distance from it.

Takes all the fun out of engineering .....

--
Click here every day to feed an animal that needs you today !!!
www.theanimalrescuesite.com/

Not if the surface completely encloses you. The MRT is solid angles weighted
by their temperatures. Multiply each area your body sees by its temp, add
the products, and divide by the total area of a reference sphere surrounding
you, containing the individual areas. You might radiate 50% to a large close
wall. As you walk away from a large wall, the near-field view factor might
still be about 50%.
And we don't need liquid helium. The MRT graph here:
http://heatkit.com/html/guide2.htm#MasonryHeating
says we can be comfy in 90 F air with 40 F walls, in a bunny-free room.
Some buildings have chilled beams and ceilings for cooling. A chilled
floor would make more sense, since warm air rises. A slow ceiling fan
with an occupancy sensor and a room temp thermostat could stir up some
floor air as needed for comfort.
Nick

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